Pick-resistant lock



Feb. 10, 1970 BAUER ETAL 3,494,158

?ICK-RESISTANT LOCK Filed Jan. 29, 1968 3 Sheets-Sheet 2 INVENTOR. &6042455 ;4. &44/52 v 577w .A &oss/NA E95 BY @in &Kekwa ATTOENEV Feb. 10, 1970 Filed Jan. 29, 1968 C. A. BAUER AL ?ICK-RESISTANT LOCK 3 Sheets-Sheet 5 III" o #,1 'Hta YMW,

INVENTOR.

01212455 A. @AL/E2 577w J. SUSSINA 5. ?Mud United States Patent O 3,494,158 PICK-RESISTANT LOCK Charles A. Baner, Woodbridge, Conn., and Stan J. Sussina, Larchmont, N.Y., assignors to Sargent & Company, New Haven, Conn., a corporation of Delaware Filed Jan. 29, 1968, Ser. No. 701,413 Int. Cl. E05b 27/00 U.S. Cl. 70-364 12 Claims ABSTRACT OF THE DISCLOSURE There is provided in a key-operated lock a lock cylinder with a key barrel rotatable therein and each having transverse tumbler pin bores, each bore in one :being alignable with a bore in the other in which bores lower and upper tumbler pins are longitudinally slidable. The upper pins may be split transversely for master-keying purposes. Each pin has a lower end face, except the lowermost or key pin, constructed and arranged with reference to the pin below it with which it is engaged, to effectively resist shifting of the axis of this upper pin when an attempt is made to pick it.

This invention relates to a pick-resistant lock, and relates more particularly to a key-operated lock of the tumbler-pin type wherein the .construction and arrangement of tumbler pins within pin bores is such as to make it extremely dilficult, at best, for one seeking unauthorized entry to pick the lock.

It is known that many key-operated, pin-tumbler locks have been designed and constructed heretofore with' the object of producing a lock construction which is very resistant to efforts to pick the same. Such constructions, for example, have included the provision of tumbler pins which fit relatively tightly in their tumbler-pin bores, that is to say, they have relatively little lateral play in these bores. However, such locks are expensive to produce, being made to very fine tolerances, and are also subject to jamming through the Sticking of tumbler pins in their Ibores due to such -factors as weather conditions and dirt or excessive graphite in the pin bores. Hence in many lock constmctions today the tumbler pins employed are so constructed and arranged with reference to their bores that they have considerable play to avoid the aforementioned difficulties and to avoid a further one not previously mentioned, which is end play of the key barrel in the lock cylinder which may cause jamming of the tumbler pins if the tumbler pins have a tight fit.

Hence in locks such as the lock of the invention tumbler pins are employed which have a more or less conventional fit within their pin bores. The pins may have for illustrative purposes an approximate diameter of .114 of an inch while the pin bores may be .124 of an inch. This obviates the difficulties mentioned above with reference to locks that jam, even when the authorized key is used in the lock as indicated above; and the construction and arrangement permits the pins to cock or tilt within their pin bores to the usual extent due to the difference of approximately .010 of an inch in the diameter of the pins and the diameter of the bores.

The present invention resides in the construction and arrangement of such tumbler pins within their bores that the axis of an upper pin with reference to the axis of a lower pin with which it is engaged resists very effectively bodily shifting movement when the pins present a shear line between the lock cylinder and the key ibarrel, which is required by Seating the upper pin on a ledge presented by the key barrel upon torsional force exerted on the 7 latter during a lock-picking attempt as the pins are raised or lowered by a picking tool.

ice

The invention resides in more detail in the provision of interengaging surfaces of adjoining tumbler pins which effects on longitudinal movement of the pins a piloting action on the upper pin so that as it reaches the shear line, which is not its normal position, lateral shifting of the lower end of the upper pin is effectively resisted during a lock-picking attempt though the upper pin may tilt or cock. This is effected by providing a protrusion on one of the pins which is received in a socket formed in the other pin. It should be noted in this connection that no claim is made \broadly such as to pins which telescope one within the other during a locking or unlocking operation nor broadly to a pin which has a protrusion received in a socket formed in another pin.

The last-mentioned construction and arrangement is shown to be old in Brantingson U.S. Patent No. 2,192,371, issued Mar. 5, 1940. The last-mentioned patent discloses the use of a plurality of tumbler pins each comprised of a plurality of stacked washer-like elements, the washers of each being free to shift laterally to some extent with reference to the others of the pin allegedly to cause jamming between the key barrel and the lock cylinder during a picking operation. The patentee noted in his disclosure that he was not the first to design a lock having pins of this type and also noted that such locks tend to jam even when the authorized key is used in the lock. In attempting to obviate this diificulty, the patentee provided, in addition to the aforementioned tumbler pins, a lower tumbler pin of solid construction having at its upper end a recess for reception of a projection on the solid upper pin engaged therewith.

However, as distinguished from the lock of the present invention, these tumbler pins have a relatively tight fit in their bores, the pins having a stated diameter of .118 of an inch in bores which are .123 of an inch in diameter. Furthermore, as distinguished from the present invention, these pins present a shear line when the key is in the lock and when the key is removed from the lock.

The pins are stated to serve two purposes, which purposes further distinguish the lock of the instant invention. One is to provide a lower pin which, when raised as by a picking tool or entry of the key in the key slot, crosses the shear line. When the key is used in the lock, this, due to the tight fit of the pins, tends to align the other pin bores in the key barrel with the pin bores in the lock cylinder to avoid jamming of the lock by said other tumbler pins. The other purpose is to obtain a detent action between the key 'barrel and the lock cylinder for upsetting sensitiveness of control of manual application to the key plug of a force for displacing the key plug relatively to the casing such as is necessary in an attempt to pick the lock As will be fully appreciated hereinafter, the construction and arrangement of lock elements in accordance with the invention is quite different and the operation of the lock is very different.

One object of the invention is to provide an improved key-operated lock of the tumbler-pin type. Another object is to provide a'lock such as characterized above wherein an upper tumbler pin is piloted by a tumbler pin below it with which it is engaged in a manner such as to tend to prevent shifting of the axis of the upper pin in a lateral direction when the pins are moved in their bores during an attempt to pick the lock. Still another object is to provide a lock in which the tumbler pins may be split for master-keying purposes and include one or more intermediate splits between the uppermost pin and the lowermost pin. A further object is to provide upper and lower tumbler pins engaged with one another in the lock, one having a protrusion at one end thereof cooperating with a O socket formed in the adjacent end of the other, which engagement permits tilting or cocking of the pins in the tumbler bores while tending to resist lateral shifting movement of the upper pin with reference to the axis of the lower pin during an attempt to pick the lock.

For a clear understanding of the invention and for purposes of comparison, there are included in the accompanying drawings figures illustrating parts of a conventional lock as well as figures illustrating the lock of the invention.

In the drawings:

FIG. 1 is an enlarged sectional view of a conventional lock taken on line 1-1 of FIG. 2;

FIG. 2 is a sectional view taken on line 2--2 of FIG. l;

FIG. 3 is a view similar to FIG. 1 illustrating parts of the lock in different positions;

FIG. 4 is a sectional view taken on line 4-4 of FIG. 8 illustrating a lock embodying the invention;

FIG. 5 is a view similar to FIG. 4 but showing parts of the lock in different positions thereof;

FIG. 6 is a View similar to FIG. 4 but illustrating a modified form of the lock;

FIG. 7 is a view similar to FIG. 6 further illustrating the modified form of the lock and showing parts thereof in different positions;

FIG. 8 is a sectional view taken on line 8 8 of FIG. 4;

FIG. 9 is a View on a smaller scale similar to FIG. 8 but showing a key inserted in the lock; and

FIG. 10 is a view similar to FIG. 5 showing the first form of the invention, illustrating parts of the lock in different positions which they occupy during rotation of the key barrel in the lock cylinder by the key.

In FIGS. l through 3 of the drawings illustrating a conventional lock, there is shown at 10 a housing or lock cylinder having a longitudinal bore 10 therein rotatably receiving a longitudinal key barrel 11 provided with suitable means to prevent axial displacement in the bore, the barrel having a key opening 12 extending longitudinally thereof and being provided at its inner end with a conventional rollback 13. As shown in FIG. 2, the key barrel is provided with a plurality of longitudinally spaced transversely directed bores 14 in communication with the key opening in the barrel, the bores extending through the periphery of the barrel. The lock cylinder 10 is provided with similar bores 15 communicating at their lower ends with the bore 10 of the cylinder, with which bores 15 corresponding bores 14 may be aligned. The upper ends of the -bores 15 may -be closed in a suitable manner.

The bores 14 in the key barrel receive lower tumbler pins 16, 17, 18, 19 and 20 respectively which are illustrated as key pins. Tumbler pins 21, 22, 23, 24 and 25 cooperate respectively with pins 16, 17, 18, 19 and 20 and occupy positions in the corresponding bores 15 formed in the lock cylinder 10. The pins which operate in the last-mentioned bores of the lock cylinder are upper pins and are urged downwardly by corresponding compression springs 26, each acting between the closed upper end of one bore 15 and the upper end of the upper pin in the bore. The upper pins through their engagement with the lower pins urge the lower pins downwardly or into the key opening of the key barrel. The mating faces of the upper and lower pins are planar.

In FIGS. 1 and 2 of the drawings the upper and lower tumbler pins are shown in longitudinal positions which they occupy when the key is removed from the lock. In these positions the upper tumbler pins extend across the shear line between the key barrel and the lock cylinder to prevent rotation of the key barrel.

FIG. 1 illustrates a torsional clockwise force exerted on the key barrel as in picking of the lock prior to raising the upper and lower tumbler pins for unauthorized entry. The pins may have a conventional diameter of approximately .114 of an inch while the bores may have a conventional diameter of .124 of an inch, the difference between the pin diameter and the bore diameter being .010. Hence the pins may shift laterally somewhat and, owing to this, there may be some play permitted between the 4 lock cylinder and the key barrel. As indicated in FIG. 1, the key barrel may be rotated by the aforementioned torsional force so that the axis of the bore 14 shown in FIG. 1 is somewhat out of alignment with the axis of the bore 15 shown in the last-mentioned View. As shown in the last-mentioned View, the upper pin 22 extends across the shear line between the lock cylinder and the key barrel, thereby locking the cylinder and the barrel together. Also as shown in this View, the pin 22 is pinched between the cylinder and the barrel due to the aforementioned torsional force on the barrel.

This pinching pressure tends to cock the pin 22 in its bore and with reference to the axis of the lower pin 17. It will be understood from the foregoing that during a picking operation pins 21, 23, 24 and 25 are acted upon in similar manner and are tilted or cocked also, the extent of the tilting or cocking depending upon the degree of tightness of each individual pin. Of course, each of pins 21, 22, 23, 24 and 25 must be picked to rotate the barrel sufficiently to operate the rollback 13. The picker conventionally attempts to pick first the tightest upper pin which for present purposes is assumed to be the pin 22. In the illustrated type of picking, the aforementioned torsional force is applied to the key barrel before the pin 17 cooperating with the pin 22 is raised by a picking tool 27 inserted below the pin 17 in the key opening 12. However, the lock may be picked by what is known as reverse picking, not shown, in which case the pins 17 and 22 are raised prior to a torsional force being exerted on the key barrel. In reverse picking, the upper and lower pins are permitted to be lowered under the influence of the spring 26 as torsional force on the key barrel is very gently released. In reverse picking the pins are also tilted or cocked as they are pinched between the cylinder and key barrel by the torsional force on the latter.

While the torsional force is applied to the key barrel and the pick 27 is inserted under the pin 17 for the purpose of picking the pin 22 in what may be termed the direct method of picking as opposed to the above-discussed reverse method of picking, the pin 17 is raised by the pick from the position of FIG. 1 toward the position of FIG. 3 while the aforementioned pinching effect on pin 22 is maintained and the latter is cocked or tilted. When the shear line is reached by raising movement of the lastmentioned pins, the pinching force on the pin 22 is suddenly released. The release of pressure on the pin 22 caused by the torsional force on the key barrel tends to cause the lower end of the pin 22 to pop or snap in a direction opposite the torsional force Which is maintained or, to put it another way, in the direction in which freedom of lateral movement of the pin 22 or its axis is suddenly permitted in the bore 15 because of the fit of the pin 22 in the last-mentioned bore. This causes the lower end of the pin to catch on the ledge 11 presented by the key barrel as shown in FIG. 3. When the axis of the pin 22 has shifted laterally in the aforementioned manner to catch on the ledge 11 presented by the key barrel, the pin 22 is picked and the lock picker proceeds to pick the remaining pins of the lock in a similar manner, being careful in so doing not to dislodge the pin 22.

The lock of the invention illustrated in FIGS. 4, 5, 8, 9 and 10 is in some respects similar in its construction to the conventional lock previously described, with like reference numerals indicating identical parts such, for example, as the lock cylinder, the key barrel, the pin bores and the driver springs. The tumbler pins may all have the same diameters and the same fit within the pin bores. The construction of the tumbler pins, however, is quite different and will be described hereinafter.

In this form of the invention the lower or key pins in the bores 14 provided in the key barrel are indicated at 28, 29, 30, 31 and 32 respectively. The lower ends of these pins may be rounded as shown. Each of these pins has a substantially flat upper end recessed in its central region or a distance from the circumference of the pin. The illustrated pins have cylindrical peripheral surfaces. One of these recesses, indicated at 29 in a pin 29, is shown to advantage in FIG. 4. This recess, like the others, has the Outline of a frustum of a cone.

The lower or key pins previously described cooperate with upper pins. In this illustrated form, which is shown by way of example only, the lower pin 28 cooperates with a single upper pin 33 and the pin 29 cooperates with a single upper pin 34. The previously described pin 30 cooperates with two upper pins which are termed splits in the industry and are employed for master-keying purposes to provide multiple shear lines, the lowermost of the lastrnentioned upper pins being indicated at 35` and the uppermost being indicated at 36. Lower or key pin 31 has above it for cooperation therewith splits 37 and 38, 37 being lowermost, while lower pin 32 has above it for cooperation therewith upper splits 39 and 40, 39 being lowermost.

The lower end of each upper pin is formed in the manner shown in FIG. 4 illustrating the upper pin 34, and all pins are biased downwardly or toward the key opening 12 by corresponding driver springs 26. The lower end of the upper pin 34 which cooperates with the pin 29 has a projection 34 which in this illustrated form has the shape of a truncated cone for reception in the complementally formed recess 29 in the lower pin 29. The lower end of the pin 34 also has an annular planar surface horizontally disposed surrounding the projection 34 and disposed intermediate the latter and the circumference of the pin 34 which has a small chamfer, not shown, at this end of the pin. In like manner the pin 29 has an annular horizontal planar surface surrounding the recess 29 horizontally arranged and disposed intermediate the recess and the circumference of the pin which also has a small chamfer, not shown, at this end of the pin. The aforementioned chamfers facilitate unlocking movement of the tumbler pins.

The aforementioned planar surface on the upper end of the pin 29, shown in FIG. 4 for example, avoids a junction of the recess 29 with the circumference or cylindrical surface of the pin 29 which would produce a knife edge, Such a knife edge would cause in the use of the lock distortion of the upper end of the pin 29 as such pins are usually constructed of relatively soft material such as brass. Such distortion would tend to cause spreading of this end of the pin, which might result in failure of the pin 29 to seat properly with reference to the lower pin stop for the pin 29 in the key barrel, and might cause even more difliculty in the operation of the lock as by catching on the lock cylinder as the pin 29 is raised. As the pin 29 is provided with the aforementioned annular surface to avoid this, the pin 34 also has the aforementioned annular mating surface.

It will be noted that the projection 34 of the upper pin does not seat on the bottom of the recess 29 formed in the lower pin 29. The projection on the upper pin is seated by means defining the side wall structure of the recess which is shown as providing a conical surface. The purpose of this is to prevent the upper and lower pins from sticking together when the key barrel has a torsional force eXerted thereon by the key to cam the upper pin 34 out of the recess 29 to operate the lock in a manner which Will appear more fully hereinafter.

It should also be noted that rotational re'straint of the key barrel on torsion being exerted thereon is not intended; and little, if any, resistance to rotation of the key barrel by the key, that is, more than in a conventional lock, is felt by the fingers of the user on the key on operation of the lock.

As best shown in FIG. 8 and as previously indicated, the key pin 30 has above it for cooperation therewith a plurality of socalled splits 35 and 36 for master-keying purposes to present multiple shear lines. More specifically, the shear lines are between the pin 30 and the pin 35 and between the pin 35 and the pin 36. While only two splits are shown in the correspondingbores 14 and 15, making a total of three pins with the key pin 30, it is to be understood that a total of five pins, including splits and the key pin, may be employed in the bore 14 and the bore 15, if desired. It will be appreciated that use of this many splits would require a very short key pin and splits having very short axial dimensions, but this is common to locks such as that shown in FIGS. 1 through 3, though no splits are shown in these views.

splits employed in locks such as that shown in the lastmentioned figures make picking of conventional locks easier for two reasons. One is, obviously, that they present to the picker more shear lines available for picking of the lock, and the `other reason is that, owing to the short axial dimensions of the splits, they tend to tilt or cock even more in the bores which they occupy than longer pins and, as previously indicated, the tilting or cocking of tumbler pins and tumbler pin bores in conventional locks as opposed to the lock of the present invention tends to make it easier for a picker to pick a lock.

It will be noted with reference to cooperating pins 30, 35 and 36 that each has a piloting action on lengthwise movement of the pins, like the pins 29 and 34 and all the other pins, with reference to the next adjacent pin, which will appear more fully hereinafter. In this connection it will be noted that the pin 30, which is the lowermost or key pin, has at its upper end a recess 30 similar to the aforementioned recess 29 in the pin 29, and that the pin 35 has a projection 35 similar to the above-described projection 34 of the pin 34. But differing from the pin 34, the pin 35 has at its upper end a recess 35 similar to the recess 29 and the pin or split 36 has at its lower end a projection 36 similar to the projection 35 As shown in FIG. 8, the projection 35 of the pin 35 is received in the recess 30 of the pin 30 and the projection 36 of the pin 36 is received in the recess 35 of pin 35. It Will be understood from the foregoing that the pin or split 35 may be considered an intermediate pin. Pins or splits 37 and 39 are also intermediate pins and formed in the same manner though, as Will be seen from the lastmentioned view, their axial dimensions are different.

It should be noted here, perhaps, that, while the concept of the invention has produced optimum results in locks employing splits for master-keying purposes, the concept is not limited to a lock employing splits.

In FIG. 9 there is shown one of a series of keys made for the lock and inserted therein to present shear lines between tumbler pins employed in the lock. FIG. 10 illustrates the camming effect which is produced on an upper pin after presenting a shear line, during rotation of the key barrel by the key, which serves to raise the upper pin out of the socket in the lower pin by the camming action of the means defining the socket in the upper end of the lower pin coacting with the cam surface provided by the projection on the lower end of the upper pin. As previously indicated, no appreciable resistance is felt by the fingers of the user of the key in rotating the barrel to effect this camming action, due to the lightness of the spring 26 urging the pins downwardly or toward the key.

The planar surface of the lower end of each pin projection reoeivable in a socket in a lower pin tends to prevent sticking of the pins on the aforementioned rotation of the key barrel by the key. Moreover, this flat surface on the projection increases the bearing area of the pin on the key barrel as the barrel is rotated, to tend to prevent grooving of the key barrel by the pin having the projection. In other words, if the downward pin projection ended in a point, it Would tend to stick in a complementally formed recess and in addition would tend to groove the key barrel during the life of the lock.

The action of the lock as one attempts to pick it will now be described. Picking of the lock may be attempted by either the previously discussed reverse method or by the method described with reference to the lock of FIGS. 1 through 3. The picking tool 27 is inserted in the key opening 12 and an attempt is made to locate the tumbler pin which has the tightest fit in the lock. For the purpose of this description, it is* assumed that the upper pin 34 has the tightest fit due to manufacturing tolerances.

The pick 27 (FIG. is inserted under the pin 29 which cooperates with the pin 34 and the pins are raised by the pick from the position of FIG. 4 toward the position of FIG. 5 as a torsional force is exerted on the key barrel in the direction of the arrow of FIG. 4. The picker hunts for the shear line between the last-mentioned pins. Due to the torsional force on the key barrel during this operation, the upper pin 34 is pinched between the key barrel 11 and the lock cylinder 10, as shown in FIGS. 4 and 5.

Both the pins 29 and 34 may cock somewhat because of this pinching effect, though the cocking movement may be somewhat less than that experienced with the previously discussed pins of the lock of FIGS. 1 through 3 due to the projection 34 of pin 34 received in socket 29 of pin 29. Due to the direction of torsional force on the key barrel, the upper end of the pin 29 would tend to cock toward the right, as viewed in FIG. 4, and the upper end of the pin 34 would tend to cock to the left, the same directions of tilt as experienced with the pins of the lock of FIGS. 1 through 3. The lock picker has little, if any, feel of the pins 29 and 30 as they present a shear line, if the same torsional force is maintained on the key barrel throughout the raising of the pins 29 and 34 to present a shear line inasmuch as the pin 34 does not tend to pop or snap onto the ledge presented by the key barrel when the shear line is reached, unlike the upper pin 22 of the lock of FIG. l. For this reason a greater torsional force must be exerted on the key barrel when the shear line is presented between the pins in order to cam the upper pin out of the socket in the lower pin, and the application of additional torsion to the key barrel at a shear line of the pins in their respective bores is largely a matter of luck as, of course, the shear line is obstructed from the picker's view.

It will be noted that the axis of the upper pin, due to the tapered configuration of the lower end thereof, must be shifted laterally to a considerable extent before the lower end of the pin 34 may seat, first on the aforementioned annular surface of the upper end of the lower pin, and then on the key barrel at 11 and it will, therefore, be understood that the coacting surfaces of the pins 29 and 34 tend to effectively resist lateral shifting movement of the axis of the pin 34 to enable the pin 34 to 'be seated on the ledge 11 presented by the key barrel. As with the lock of FIG. 1, the picker, if he is successful in picking the tightest pin, must thereafter pick the remaining pins without dislodging the picked pin or pins.

It should !be noted that the split pins, particularly the intermediate pins, which may have very short axial dimensions, also tend to resist axial shifting in the aforementioned manner though they may cock or tilt during a picking action to a greater degree than the longer pin 34. This feature is especially useful where a total of four or five pins in a single stack, including splits, are employed. As previously indicated, in such instances each intermediate pin coacts with the socketed pin below it and itself provides a socket for the pin above it. It should also be noted that the projection on the pin 34 and the socket in the pin 29 may not be reversed with reference to these pins. If this were done, the lock would not be workable, that is, the projection would extend beyond the shear line and interfere with rotation of the key barrel. However, this reversal is possible in the form of the invention shown in FIGS. 6 and 7 wherein the projection received in a socket is depressible to move out of the socket and within the periphery of the key barrel.

In the modified form of the invention shown in the last-mentioned views, like reference numerals indicate identical parts. All parts may be alike except for the tumbler pins. In the last-mentioned views only a single upper pin and a single lower pin, cooperating with the upper pin, are shown to simplify and shorten the disclosure, but it should be understood that the lock may incorporate a plurality of pins similar to the illustrated upper and lower pins. i

In the form of FIGS. 6 and 7, the substantially hollow body of the lower pin is indicated at 42, which is shown as having a closed, substantially flat interior bottom surface and which is open at the mouth or other end of the lower or key pin. A plunger is longitudinally slidable in the hollow body of the pin 42 and has a projection extensible without the hollow body, the plunger being held captive in the body after assembly of the plunger in the hollow body by staking the upper end of the pin body to present a shoulder forming an abutment to limit movement of the plunger in one axial direction, i.e., in a direction to project from the pin body. The last-mentioned shoulder is indicated at 43, and the plunger at 44. The plunger is urged in the direction to project from the hollow body 42 by a compression spring 45 interposed between the bottom of the plunger and the bottom of the hollow body. The plunger has an enlargement 46 at the lower end thereof which cooperates with the aforementioned shoulder 43 of the pin body.

The Composite lower pin previously described has an upper end surface configuration similar to the lower end configuration, say, of the pin 34, for example, when the plunger is fully extended and the projection 44 thereof is received in a socket 48 in the pin 48 which is similar to the socket formed in, say, the pin 29 previously described. Both the upper and lower pins have annular mating surfaces such as those described with reference to the form of the invention shown in FIG. 4, and the pins which may be cylindrical, may also be chamfered on their circumferences at the interengaging ends of the pms.

The operation of the lock of FIGS. 6 and 7 is identical to that of the form of FIG. 4 except that the projection provided on one pin for reception in a socket in the other is retractable within the former. It will `be apparent from the foregoing that, if desired, the retractable plunger could be provided on the lower end, not shown, of an upper pin to cooperate with a socket formed in a pin directly below it. It will be further appreciated that, while the tumbler pins of the lock of FIGS. 6 and 7 are similar in some respects to the tumbler pins of the form of FIG. 8, they are not equivalents of each other.

In the form of the lock of FIG. 6, splits would not be likely to be employed, constructed so as to have a movable plunger therein because of dimensional limitations. However, it would be perfectly possible to employ, not shown, a solid split having a socket in the lower end thereof and having a projection at the upper end thereof received in a socket of another pin above it similar to the socket of the former.

Of course, it will be appreciated that all pins of a particular lock need not have the interengaging surface features of the tumbler pins of the invention. In other words, conventional pins could be employed in a lock incorporating a plurality of pins including those having the features of the invention.

While two forms of the lock have been shown in the drawings and described above, it will be apparent to those versed in the art that the invention may take other forms and is susceptible of various changes in details without departing from the principles of the invention. As one example of this, it may be noted that the tumbler pins of the lock might be of a noncylindrical shape.

What we claim is:

1. A key-operated pick-resistant lock comprising a housing having a `bore, a key barrel rotatably mounted in said bore, the key barrel having a key slot and a plurality of transverse tumbler pin bores extending through the periphery thereof and in communication with said key slot, said housing having a plurality of tumbler pin bores alignable respectively with said firstmentioned tumbler bores, a. plurality of tumbler pins extensible into said barrel tumbler bores, a plurality of tumbler pins extensible into said housing tumbler bores and spring biased in the direction of the key barrel for cooperation with corresponding ones of the pins in the barrel bores, at least one pair of said tumbler pins having means at interengaging ends thereof, presenting a shear line, for piloting these pins as they are raised or lowered with reference to the line of division between the housing and the key barrel, said coacting ends of the last-mentioned pins when the key is not in the lock being spaced from said line of division so that a pin extends across the shear line to angularly lock the key barrel to said housing, said piloting means including the last-mentioned end of one of said pair having a tapered protrusion extending therefrom received in means defining a socket formed in the near end of the other of said pair of pins which protrusion, when the key is in the lock and the pins present a shear line and a torsional force is applied to the key barrel through the key, is cammed out of the socket by the torsional force on the key barrel so as to permit rotation of the barrel in said housing to effect operation of the lock, said pin of said pair having a protrusion thereon also having a planar annular surface disposed circumferentially of said protrusion at the base thereof, said pin of said pair having means defining a socket also having a planar annular surface disposed circumferentially of said socket, said annular surfaces engaging one another when said protrusion is in said socket, the last-mentioned pins having circumferential dimensions, with reference to bore diameter, to permit a relatively loose fit of the pins through which these pins may tilt or cock, said coacting pin protrusion and means defining a pin socket acting to pilot each pin end of the pair with reference to the other as they are raised or lowered to inhibit lateral shifting movement of the uppermost one of these two pins such as would enable a lock picker to rest the lower end of the last-mentioned pin on a ledge presented by the key barrel on torsional force exerted on the latter.

2. A key-operated pick-resistant lock as defined in claim 1 wherein one of said pair of tumbler pins con-- stitutes a key pin and the other of the pair is the pin which normally extends across the shear line.

3. A key-operated pick-resistant lock as defined in claim 1 wherein said pin protrusion is formed on the upper pin and the means defining the pin socket formed on the lower pin of the pair.

4. A key-operated pick-resistant lock as defined in claim 1 wherein said pin protrusion is formed on the lower pin and the means defining the pin socket formed on the upper pin of the pair.

5. A key-operated pick-resistant lock as defined in claim 1 wherein said uppermost pin of the pair is the sole driving pin and the pin below it is the sole key pin.

6. A key-operated pick-resistant lock as defined in claim 1 wherein one of said pair of tumbler pins constitutes a key pin and the other of the pair is the pin which normally extends across the shear line, the pin protrusion being formed on the upper pin and the means defining the pin socket being formed on the lower pin of the pair.

7. A key-operated pick-resistant lock as defined in claim 1 wherein both pins of said pair are of solid construction with the exception of said socket, said socket being relatively shallow.

8. A key-operated pick-resistant lock as defined in claim 1 wherein said uppermost pin of said pair is a split pin and has above it a pin having a protrusion at its lower end received in means defining a socket in the upper end of the uppermost pin of said pair, so that each of the three pins has a piloting action with reference to the pin with Which it is engaged.

9. A key-operated pick-resistant lock as defined in claim 1 wherein said protrusion on one pin of said pair is formed by a spring-biased plunger extensible from a hollow body of the latter.

10. A key-operated pick-resistant lock as defined in claim 1 wherein said protrusion on one pin of said pair is formed by a spring-biased plunger extensible from a hollow body of the latter, the last-named pin being the lower pin of the pair.

11. A key-operated pick-resistant lock comprising a housing having a bore, a key barrel rotatably mounted in said bore, the key barrel having a key slot and a plurality of transverse tumbler bores extending through the periphery thereof and in communication with said key slot, said housing having a plurality of tumbler pin bores alignable respectively with said first-mentioned tumbler bores, a plurality of lower tumbler pins extensible into said barrel tumbler bores, a plurality of tumbler pins extending into said housing tumbler bores and spring biased in the direction of the key barrel for cooperation with the respective lower pins, one tumbler pin in each barrel bore and one tumbler pin in the corresponding housing bore forming a pair of pins having means at interengaging ends thereof, presenting a shear line, for piloting these pins within the corresponding bores as they are raised or lowered with reference to the line of division between the housing and the key barrel, said coacting ends of the last-mentioned pins when the key is not in the lock being spaced from said line of division so that one pin of the pair extends across the line to angularly lock the key barrel to the housing, said piloting means including one of said pair having a tapered protrusion extending therefrom received in means defining a socket formed in the near end of the other of said pair of pins which protrusion, when the key is in the lock and the pins present a shear line and torsional force is applied to the key barrel through the key, is cammed out of the socket by the torsional force on the key barrel, so as to permit rotation of the barrel in said housing, said pin of said pair having a protrusion thereon also having a planar annular surface disposed circumferentially of said protrusion at the base thereof, said pin of said pair having means defining a socket also having a planar annular surface disposed circumferentially of said socket, said annular surfaces engaging one another when said protrusion is in said socket, the lastmentioned pins having circumferential dimensions, with reference to the means defining the bores which they occupy, to permit a relatively loose fit of the pins with which fit these pins may tilt or cock in the bores, said coacting pin protrusion and means defining a pin socket acting to pilot said pin ends of the pair with reference to each other as they are raised or lowered to inhibit lateral shifting movement of the lower end of said upper pin such as would enable a lock picker to rest the lower end of the upper pin on a ledge presented by the key barrel on torsional force exerted on the latter.

12. A key-operated pick-resistant lock as defined in claim 11 wherein said upper pin of one of said pairs is a split pin and has above it a pin which forms with said upper pin a pair of pins having means at interengaging ends thereof for presenting a shear line, for piloting these pins as they are raised or lowered with reference to the line of division between the housing and the key barrel, the last-mentioned interengaging means comprising a protrusion on one pin of the last-mentioned pair received in means defining a socket in the other pin of the last-mentioned pair.

References Cited UNITED STATES PATENTS 2,192,371 3/1940 Brantingson 70-364 3,190,093 6/1965 Schlage 70-383 3,320,781 5/1967 Hill 70--384 3,393,542 7/1968 Crepinsek 70 358 MARVIN A. CHAMPION, Primary Examiner R. L. WOLFE, Assistant Examiner -U.S. Cl. X.R. 70-378, 421 

